The present invention relates to a semiconductor light-emitting device of which structure is inexpensively cope with a light-emitting part of an encoder that is requiring high resolving power.
There are known, as a photo-encoder using an optical device, a linear encoder for detecting a moving velocity of an object and a rotary encoder for detecting a rotating angle. The optical devices for such photo-encoders includes an example using a semiconductor light-emitting device such as a light-emitting diode (LED) in the light-emitting part and a semiconductor light-receiving device such as a photodiode in the light-receiving part.
FIG. 10 is a front view of a scheme showing one example of the LED. In FIG. 10, 1 is an LED element, 2, 3 are a pair of lead terminals and 4 is a metal wire. One electrode la of the LED element 1 is connected with the metal wire 4. The metal wire 4 is electrically connected to a lead terminal 3 by wire bonding.
Meanwhile, although not shown, an electrode is formed on the LED element 1 at a side opposite to the electrode 1a. This electrode is electrically connected onto the lead terminal 2 by die bonding. Numerical reference 5 shows a mold part formed of a light-transmissive resin to encapsulate the LED element 1 and metal wire 4. In this manner, an LED 20 for an encoder is formed. This LED 20 is structured to emit an infrared ray, for example.
FIG. 11 is an explanatory view showing an example using an LED 20 structured in FIG. 10 as a linear encoder. In FIG. 11, 10 shows an optical system using a lens, in which the numerical reference 11 is a rectangular measuring plate forming a multiplicity of slits a-n, the numerical reference 12 is a light-receiving part using a light-receiving element such as a photodiode, the numerical reference 13 is a signal line, and the numerical reference 14 is a signal processing section.
The LED 20 operable as a surface light source. The LED 20, at a mold part 5 close to a light-emitting surface, emits an output light having a width Lx. The optical system 10 focuses the output light having a width Lx emitted from the LED 20 and converts it into spot light sources to travel as a luminous flux toward the light-receiving part 12.
When the measuring plate 11 is moved in the arrow direction A, the light-receiving part 12 receives and blocks light depending upon a presence or absence of a slit a-N formed in the measuring plate 11. The signal received or blocked by the light-receiving part 2 is properly processed in the signal processing section 4 to form a pulse waveform. By counting pulses in one period, it is possible to detect a moving velocity of the measuring plate 11.
In place of the rectangular measuring plate 11 moving linearly, a rotary encoder can be structured to detect a rotating angle of a rotary plate by arranging a rotary plate, for rotation, circumferentially forming a multiplicity of slits between the optical system 10 and the light-receiving part 12 and properly processing, in the signal processing section 14, the signal received or blocked by the light-receiving part 12.
In this manner, in the conventional encoder, the output light emitted from a semiconductor light-emitting device having a surface light source, such as an LED, is focused by the optical system and converted into spot light sources. However, in order for conversion into precise spot light sources, the optical system must use a multiplicity of lenses. There has been a problem with increased cost.
The luminous flux in a state not converted into spot light sources, if made to travel toward the measuring plate, results in worsened resolution. In particular, there has been a problem of the impossibility to cope with an encoder having a fine slit formed in the measuring plate to form a signal by receiving and blocking a luminous flux thereby performing signal processing with resolution. Meanwhile, spot light sources for an encoder can be obtained by laser light. In this case, there has been a problem of cost increase.
The present invention has been made in view of such problems, and it is an object to provide a semiconductor light-emitting device applicable as an encoder linear light source by a simple structure.
Also, it is an object to provide a semiconductor light-emitting device structured, to inexpensively cope with, as an encoder light-emitting part requiring high resolving power.
The foregoing object of the present invention is achieved by a semiconductor light-emitting device comprising: a semiconductor light-emitting element, a light-transmissive resin mold part encapsulating the semiconductor light-emitting element, and converting means for converting an output light from the semiconductor light-emitting element into a linear light source to be emitted.
Also, desirably, the converting means is a light blocking member having a slit and structured to emit an output light passed through the slit.
Also, desirably, the converting means is arranged on a light-emitting surface of the semiconductor light-emitting element and a light blocking member having a slit, the resin mold part encapsulating the light blocking member together with the semiconductor light-emitting element.
Also, desirably, the light blocking member is a metal plate having a slit.
Also, desirably, the metal plate is extended from the resin mold part and bent to along an outer surface of the resin mold part.
Also, desirably, the converting means is structured by a resin mold part of a light-transmissive resin, the resin mold part has a slit in a region corresponding to a light-emitting surface of the semiconductor light-emitting element and structured to derive light of the semiconductor light-emitting element through the slit. Also, desirably, the semiconductor light-emitting element at a surface is covered with the light-transmissive resin.
Also, desirably, the converting means is a die pad having a slit, the semiconductor light-emitting element being firmly fixed, face down, on the die pad by using a light-transmissive insulation resin.
Also, desirably, the semiconductor light-emitting device is structured to emit light at a side surface.
Also, desirably, the converting means is a light blocking member having a slit attached on an outside of the resin mold part.
Also, the converting means is a cover forming a slit, the cover being fitted on a light-emitting surface of the semiconductor light-emitting element and encapsulated by the mold part of a light-transmissive resin to emit the output light passed the slit.
According to the above feature, there is provided the converting means for emitting the output light of the surface light source by converting it into a linear output light. Consequently, because the structure is simple and moreover a fine, linear light source is obtained, the semiconductor light-emitting device can be applied as a light source of an encoder.
Meanwhile, in the invention, the semiconductor light-emitting device after fitted with a cover forming a slit in a light-emitting surface is encapsulated by a mold part of a light-transmissive resin material. Consequently, the cover is firmly fixed by the mold part without causing positional deviation. Also, there undergoes no affection due to positional deviation in the LED element during die bonding. Accordingly, linear output light can be emitted with accuracy.
Furthermore, the foregoing object of the invention is achieved by a structure of a semiconductor light-emitting device comprising: a semiconductor light-emitting element forming, on a side surface, a light-emitting layer to be used as a light source of a linear light source and a mold part formed of a light-transmissive resin encapsulating the semiconductor light-emitting element, wherein a lens is formed outwardly projecting in a dome form in a surface of the mold part where an output light is to be emitted from the light source of the linear light source toward a light receiving part, the light source of the linear light source being converted by the lens into a multiplicity of light sources of spot light sources to emit a collimate output light at the spot light sources in multiplicity formed on the lens.
Meanwhile, preferably, the linear light source is a linear member arranged to pass a focal point of the lens.
According to the above feature of the invention, a lens is formed by a mold part of a light-transmissive resin material. This lens converts the light source of a linear light source into a multiplicity of light sources of spot light sources. Because a collimate output light is emitted from the spot light sources in multiplicity formed on the lens, when a measuring plate forming fine slits is moved, the light-receiving part can receive or block light with accuracy. Accordingly, the semiconductor light-emitting device can be coped with as a light-emitting part of an encoder requiring signal processing with resolution.
By arranging the linear light source to pass a focal point of the lens, it is possible to obtain a further preferred collimate light source.